Weihai Sun

CuSCN-Based Inverted Planar Perovskite Solar Cell with an Average PCE of 15.6%

Although inorganic hole-transport materials usually possess high chemical stability, hole mobility, and low cost, the efficiency of most of inorganic hole conductor-based perovskite solar cells is still much lower than that of the traditional organic hole conductor-based cells. Here, we have successfully fabricated high quality CH3NH3PbI3 films on top of a CuSCN layer by utilizing a one-step fast deposition-crystallization method, which have lower surface roughness and smaller interface contact resistance between the perovskite layer and the selective contacts in comparison with the films prepared by a conventional two-step sequential deposition process. The average efficiency of the CuSCN-based inverted planar CH3NH3PbI3 solar cells has been improved to 15.6% with a highest PCE of 16.6%, which is comparable to that of the traditional organic hole conductor-based cells, and may promote wider application of the inexpensive inorganic materials in perovskite solar cells.

Solution-Processed CuS NPs as an Inorganic Hole-Selective Contact Material for Inverted Planar Perovskite Solar Cells

Organic-inorganic hybrid perovskite solar cells (PSCs) have drawn worldwide intense research in recent years. Herein, we have first applied another p-type inorganic hole-selective contact material, CuS nanoparticles (CuS NPs), in an inverted planar heterojunction (PHJ) perovskite solar cell. The CuS NP-modification of indium tin oxide (ITO) has successfully tuned the surface work function from 4.9 to 5.1 eV but not affect the surface roughness and transmittance, which can effectively reduce the interfacial carrier injection barrier and facilitate high hole extraction efficiency between the perovskite and ITO layers. After optimization, the maximum power conversion efficiency (PCE) has been over 16% with low J-V hysteresis and excellent stability. Therefore, the low-cost solution-processed and stable CuS NPs would be an alternative interfacial modification material for industrial production in perovskite solar cells.

A Strategy to Simplify the Preparation Process of Perovskite Solar Cells by Co‐deposition of a Hole‐Conductor and a Perovskite Layer

The feasibility of co-depositing a hole-conductor and a perovskite layer is demonstrated to simplify the preparation process of perovskite solar cells. The CuSCN incorporated in the perovskite layer can participate in forming the perovskite/CuSCN bulk-heterojunction and accelerate hole transport effectively, which eventually leads to a maximum power conversion efficiency of 18.1% with almost no J-V hysteresis.

Mixed‐Organic‐Cation Tin Iodide for Lead‐Free Perovskite Solar Cells with an Efficiency of 8.12%

Abstract In this work, a fully tin‐based, mixed‐organic‐cation perovskite absorber (FA)x(MA)1− xSnI3 (FA = NH2CH = NH2 +, MA = CH3NH3 +) for lead‐free perovskite solar cells (PSCs) with inverted structure is presented. By optimizing the ratio of FA and MA cations, a maximum power conversion efficiency of 8.12% is achieved for the (FA)0.75(MA)0.25SnI3‐based device along with a high open‐circuit voltage of 0.61 V, which originates from improved perovskite film morphology and inhibits recombination process in the device. The cation‐mixing approach proves to be a facile method for the efficiency enhancement of tin‐based PSCs.

Hole-conductor-free planar perovskite solar cells with 16.0% efficiency

In the present work, a hole-conductor-free inverted-structure planar perovskite solar cell was fabricated by a solution process. Remarkably, the device showed a power conversion efficiency (PCE) up to 16.0%, which is higher than those of reported hole-conductor-free perovskite solar cells, and even higher than that of devices using NiOx as the hole conductor. Furthermore, the hole-conductor-free device was also found to reveal a very good stability.

High-performance hybrid perovskite solar cells with polythiophene as hole-transporting layer via electrochemical polymerization†

Thin polythiophene film prepared via electrochemical polymerization has been successfully used as the hole-transporting layer in CH3NH3PbI3 perovskite solar cells, affording a series of ITO/polythiophene/CH3NH3PbI3/C60/BCP/Ag devices. The highest occupied molecular orbit (HOMO) and lowest unoccupied molecular orbit (LUMO) of the polythiophene film are determined as −5.20 eV and −3.12 eV, respectively, which match well with that of CH3NH3PbI3 perovskite material. In addition, a promising power conversion efficiency of 11.8%, featuring a high fill factor of 0.707, good open voltage of 1.03 V and short current density of 16.2 mA cm−2, has been obtained, which renders polythiophene as an effective competitor to spiro-OMeTAD in perovskite solar cells. Furthermore, this work provides a simple, prompt, controllable and economic approach for the preparation of hole-transporting layer, which would undoubtedly yield new insight into the industrial production of perovskite solar cells.

A Breakthrough Efficiency of 19.9% Obtained in Inverted Perovskite Solar Cells by Using an Efficient Trap State Passivator Cu(thiourea)I

It is extremely significant to study the trap state passivation and minimize the trap states of perovskite to achieve high-performance perovskite solar cells (PSCs). Here, we have first revealed and demonstrated that a novel p-type conductor Cu(thiourea)I [Cu(Tu)I] incorporated in perovskite layer can effectively passivate the trap states of perovskite via interacting with the under-coordinated metal cations and halide anions at the perovskite crystal surface. The trap state energy level of perovskite can be shallowed from 0.35-0.45 eV to 0.25-0.35 eV. In addition, the incorporated Cu(Tu)I can participate in constructing the p-i bulk heterojunctions with perovskite, leading to an increase of the depletion width from 126 to 265 nm, which is advantageous for accelerating hole transport and reducing charge carrier recombination. For these two synergistic effects, Cu(Tu)I can play a much better role than that of the traditional p-type conductor CuI, probably due to its identical valence band maximum with that of perovskite, which enables to not only lower the trap state energy level to a greater extent but also eliminate the potential wells for holes at the p-i heterojunctions. After optimization, a breakthrough efficiency of 19.9% has been obtained in the inverted PSCs with Cu(Tu)I as the trap state passivator of perovskite.

Solution processed inorganic V2Ox as interfacial function materials for inverted planar-heterojunction perovskite solar cells with enhanced efficiency

An inverted planar heterojunction perovskite solar cell (PSC) is one of the most competitive photovoltaic devices exhibiting a high power conversion efficiency (PCE) and nearly free hysteresis in the voltage–current output. However, the band alignment between the transport materials and the perovskite absorber has not been optimized, resulting in a lower open-circuit voltage (Voc) than that of regular PSCs. To address this issue, we tune the band alignment in perovskite photovoltaic architecture by introducing bilayer structured transport materials, e.g., the hole transport material poly(ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)/V2O5. In this study, solution processed inorganic V2Ox interlayer is incorporated into PEDOT:PSS for achieving improved film surface properties as well as optical and electrical properties. For example, the work function (WF) was changed from 5.1 to 5.4 eV. A remarkably high PCE of 17.5% with nearly free hysteresis and a stabilized efficiency of 17.1% have been achieved. Electronic impedance spectra (EIS) demonstrate a significant increase in the recombination resistance after introducing the interlayer, associated with the high Voc output value of 1.05 V. Transient photocurrent and photovoltage measurements indicate that a comparable charge transport process and an inhibited recombination process occur in the PSC with the introduction of the V2Ox interlayer.

High-performance cadmium sulphide-based planar perovskite solar cell and the cadmium sulphide/perovskite interfaces

Abstract. Planar heterojunction perovskite solar cell is one of the most competitive photovoltaic technologies, while charge transport materials play a crucial role. We successfully demonstrated an effective electron transport material, namely chemical bath deposited cadmium sulphide (CdS) film under low temperature, in perovskite-based solar cells. Power conversion efficiency of 16.1% has been achieved, which is comparable to that of devices based on TiO2 film prepared via low-temperature processes. Electronic impedance spectra reveal that the CdS-based device presents a higher recombination resistance than TiO2-based devices, which reduces carrier recombination and increases the open circuit voltage. The interface between CdS and perovskite was characterized with improved characteristics when compared to TiO2, e.g., efficient carrier extraction and reduced surface defect–associated degradation in the devices, which help to alleviate anomalous hysteresis and long-term instability. Furthermore, the entire device was fabricated via solution process with a processing temperature below 100°C, suggesting a promising method of further development of perovskite solar cells and commercial manufacturing.

The Dawn of Lead‐Free Perovskite Solar Cell: Highly Stable Double Perovskite Cs2AgBiBr6 Film

Abstract Recently, lead‐free double perovskites have emerged as a promising environmentally friendly photovoltaic material for their intrinsic thermodynamic stability, appropriate bandgaps, small carrier effective masses, and low exciton binding energies. However, currently no solar cell based on these double perovskites has been reported, due to the challenge in film processing. Herein, a first lead‐free double perovskite planar heterojunction solar cell with a high quality Cs2AgBiBr6 film, fabricated by low‐pressure assisted solution processing under ambient conditions, is reported. The device presents a best power conversion efficiency of 1.44%. The preliminary efficiency and the high stability under ambient condition without encapsulation, together with the high film quality with simple processing, demonstrate promise for lead‐free perovskite solar cells.