Yueyong Yang

An all-carbon counter electrode for highly efficient hole-conductor-free organo-metal perovskite solar cells

An all-carbon counter electrode has been fabricated for hole-conductor-free organo-metal perovskite heterojunction thin-film solar cells by a simple and low-temperature process. The counter electrode consisted of two parts: a mesoscopic carbon layer for good contact with the perovskite layer, and a piece of industrial flexible graphite sheet as the conducting electrode. Several types of carbon materials were employed in the counter electrodes and tested. From an electrochemical impedance study, it is found that the contact between the counter electrode and perovskite layer has a significant influence on the charge transport properties of the cells. A power conversion efficiency up to 10.2% has been achieved by hole-conductor-free mesoscopic CH3NH3PbI3/TiO2 heterojunction solar cells with the counter electrode containing a composition of graphite and carbon black, which inspires a new promising route towards low-cost and large-scale commercialization of perovskite solar cells.

Composite counter electrode based on nanoparticulate PbS and carbon black: towards quantum dot-sensitized solar cells with both high efficiency and stability.

PbS/carbon black (CB) composite counter electrode (CE) has been fabricated by a low cost and low temperature processable method using the wet chemistry synthesized PbS nanoparticles. The nanosized PbS in the composite CE provides a large area of catalytic sites, and the chain-type CB framework acts as an excellent electrical tunnel for fast electron transport from an external circuit to highly catalytic PbS nanoparticles. The optimized PbS/CB composite CE shows a charge transfer resistance (R(CT)) as low as 10.28 Ω cm², which is an order of magnitude lower than the value obtained in the previous study on pure PbS CE. The CdS/CdSe quantum dot-sensitized solar cells with the PbS/CB composite CE achieve a photovoltaic conversion efficiency of 3.91% and no degradation of the efficiency over 1000 h under room conditions.

Investigation on New CuInS2/Carbon Composite Counter Electrodes for CdS/CdSe Cosensitized Solar Cells

The search for semiconductor-sensitized solar cell (SSC) counter electrode alternatives has been a continuous effort and long ongoing work, while the studies in counter electrode kinetic performance and stability are important to improve the overall efficiency. Here, a ternary chalcopyrite compound CuInS2 is first employed as counter electrode (CE) material for CdS/CdSe cosensitized solar cells. Besides, in order to increase the electron transfer activity at the counter electrode/electrolyte interface and stability, an appropriate amount of active carbon/carbon black mixture is introduced to afford CuInS2/carbon composite electrodes. Electron transfer processes in CuInS2-based electrodes are investigated in detail with the aid of electrochemical impedance spectroscopy and I-E measurement. Up to 4.32% of the light-to-electricity conversion efficiency has been achieved for the CdS/CdSe SSCs with the CuInS2/carbon composite electrode. Besides, a preliminary long-term stability test reveals that the new CuInS2/carbon composite counter electrode exhibits good stability after being kept in the dark at room temperature and without current flow for 1000 h.

Pressure-assisted CH3NH3PbI3 morphology reconstruction to improve the high performance of perovskite solar cells

The pressure is introduced as a parameter in the post-treat process for perovskite solar cells. Via a hot-pressing method, the rough surface of perovskite film becomes smooth, and the pin-holes can be cured. This modified perovskite morphology can help to improve charge transporting and eliminate recombination in the perovskite solar cells. Moreover, significantly enhanced photovoltaic performances with high PCEs of 10.84% and 16.07% are thus achieved in HTM-free type and spiro-OMeTAD based cells, respectively.

Panchromatic Quantum‐Dot‐Sensitized Solar Cells Based on a Parallel Tandem Structure

A tandem-structure sensitized solar cell, comprising different inorganic semiconductor quantum dots (QDs) as sensitizers in two different compartments, has been designed for the first time with the aim of extending the light-absorption range of current technologies. In this system, the CdS/CdSe co-sensitized quantum-dot solar cell (QDSC) is in the upper part, whereas the PbS/CdS co-sensitized QDSC is in the lower part; these are connected in parallel with each other. In the middle of the tandem solar cell, a Cu2 S mesh counter electrode is employed. By optimizing the electrode thickness and QD-deposition time, short-circuit photocurrent density values of as high as 25.12 mA cm(-2) have been achieved; this value is nearly equal to the sum of the two constituent QD-sensitized devices and gives rise to a solar power-conversion efficiency of 5.06 %.

The influence of different mask aperture on the open-circuit voltage measurement of perovskite solar cells

We studied the influence of different mask apertures on the open-circuit voltage measurement of perovskite solar cells. Aperture masks with different sizes were equipped to control the proportion of dark-state region. Statistical results of photovoltaic parameters, ideality factor, and reverse saturation current density revealed that different mask apertures would affect the J-V measurement results, especially the open-circuit voltage. A double diode model simulation together with the impedance spectroscopy and transient photovoltage decay measurement has been further employed to analyze the reasons and found that the mask with inappropriate shading, which is smaller than the cells active area, will introduce excess charge transfer and recombination pathways, thus lead to an underestimate of open-circuit voltage. This work provides a promising route towards a more accurate J-V measurement of perovskite solar cells.