Manoj Jaysankar

Pinhole-free perovskite films for efficient solar modules

We report on a perovskite solar module with an aperture area of 4 cm2 and geometrical fill factor of 91%. The module exhibits an aperture area power conversion efficiency (PCE) of 13.6% from a current–voltage scan and 12.6% after 5 min of maximum power point tracking. High PCE originates in pinhole-free perovskite films made with a precursor combination of Pb(CH3CO2)2·3H2O, PbCl2, and CH3NH3I.

Rapid composition screening for perovskite photovoltaics via concurrently pumped ultrasonic spray coating

Transitioning perovskite photovoltaics from the rapid progress in lab-scale devices to industrially viable large area modules is a key challenge for the economic breakthrough of the technology. In this work, we demonstrate ultrasonic spray coating as a scalable and versatile linear deposition technique for high efficiency perovskite photovoltaics. We show the versatility of concurrently pumped ultrasonic spray coating by rapidly and precisely optimizing precursor ratios based on PbCl2, Pb(CH3CO2)2·3H2O, PbBr2, CH3NH3Br, and CH3NH3I to achieve highly crystalline and pinhole-free layers. Initial power conversion efficiencies of 15.7% for small scale devices and 11.7% for 3.8 cm2 modules were achieved with current–voltage sweeps and tracked to 13.4% for devices and 10.4% for modules under continuous illumination and bias at the maximum power point. Process versatility is further demonstrated with the in situ bandgap control in CH3NH3PbIXBr3−X layers.

Crystallisation dynamics in wide-bandgap perovskite films

Organic–inorganic metal halide perovskite materials have evolved as highly efficient photovoltaic materials with a controllable range of bandgaps. This trait offers exciting prospects for the application of perovskites as wide-bandgap thin-film top solar cells in tandem architectures with crystalline silicon bottom solar cells. In this work, we present a systematic material study on spin-coated methylammonium lead trihalide (CH3NH3Pb(I0.6Br0.4)3) that has a band gap of 1.77 eV, optimal for tandem architectures with crystalline silicon. Using a combination of X-ray diffraction, time-resolved photoluminescence, and scanning electron microscopy techniques, we determine the strong impact of annealing temperature and duration on perovskite film crystallinity, carrier lifetime, and average grain size. We further demonstrate a clear correlation between solar cell performance and crystallisation dynamics in the perovskite films. With optimised crystallisation of the perovskite films, our solar cells exhibit peak power conversion efficiency of 10.6% that stabilises at 9.0% after 10 minutes of maximum power point tracking. Finally, the activation energy for grain boundary mobility, and grain growth exponents are determined via quantitative analysis of grain growth kinetics, and hence, perovskite film quality.

Scalable perovskite/CIGS thin-film solar module with power conversion efficiency of 17.8%

All-thin film perovskite/CIGS multijunction solar modules, combining a semi-transparent perovskite top solar module stacked on a CIGS bottom solar module, are a promising route to surpass the efficiency limits of single-junction thin-film solar modules. In this work, we present a scalable thin-film perovskite/CIGS photovoltaic module with an area of 3.76 cm2 and a power conversion efficiency of 17.8%. Our prototype outperforms both the record single-junction perovskite solar module of the same area as well as the reference CIGS solar module. The presented perovskite/CIGS thin-film multijunction solar module makes use of the “4-terminal architecture”, which stacks the perovskite solar module in superstrate configuration on top of the CIGS solar module in substrate configuration. Both submodules apply a scalable interconnection scheme that can accommodate scale-up towards square meter scale thin-film multijunction solar modules. In order to identify the future potential of the presented stacked perovskite/CIGS thin-film solar module, we quantify the various losses in the presented prototype and identify the key challenges of this technology towards very high power conversion efficiencies.

Low-cost electrodes for stable perovskite solar cells

Cost-effective production of perovskite solar cells on an industrial scale requires the utilization of exclusively inexpensive materials. However, to date, highly efficient and stable perovskite solar cells rely on expensive gold electrodes since other metal electrodes are known to cause degradation of the devices. Finding a low-cost electrode that can replace gold and ensure both efficiency and long-term stability is essential for the success of the perovskite-based solar cell technology. In this work, we systematically compare three types of electrode materials: multi-walled carbon nanotubes (MWCNTs), alternative metals (silver, aluminum, and copper), and transparent oxides [indium tin oxide (ITO)] in terms of efficiency, stability, and cost. We show that multi-walled carbon nanotubes are the only electrode that is both more cost-effective and stable than gold. Devices with multi-walled carbon nanotube electrodes present remarkable shelf-life stability, with no decrease in the efficiency even after 180 ...

Perovskite–silicon tandem solar modules with optimised light harvesting

Perovskite–silicon tandem solar cells are potentially attractive, inexpensive solutions to surpass the power conversion efficiency limits of market-leading silicon solar cells. While such tandem solar cells have been demonstrated to reach high efficiencies, they require advanced light management to utilise the solar spectrum efficiently. Moreover, area upscaling with minimal optical losses is necessary to transfer the properties of lab scale devices to commercial scale products. Here, we demonstrate four-terminal perovskite–silicon tandem solar modules with efficient light management. With rigorous optical simulations of the complete tandem stack, we design light management concepts that minimise overall reflection and enhance complementary absorption of the subcells. The optical optimisation results in four-terminal tandem power conversion efficiencies of 25.3% on 0.13 cm2 and 23.9% on 4 cm2, both exceeding the stand-alone silicon solar cell power conversion efficiency of 23.0%.

Translucent, color-neutral and efficient perovskite thin film solar modules

Thin film perovskite photovoltaic devices combine high power conversion efficiencies with low weight, large area, high speed production capabilities and high versatility in form factor. With this paper, an additional feature is added to the device property portfolio: optical transparency. Results on translucent perovskite modules with selectively tuned levels of transparency are reported by applying the industrially established fabrication process of partial area ablation to high efficiency opaque devices. After process completion, the final devices consist of opaque areas that absorb the light, and transparent areas that permit neutral light transmission. We compare the effectiveness of using two active area removal techniques: mechanical scribing and laser ablation, and determine the factors that limit the maximum transparency and power conversion efficiency. Moreover, we show how the choice of the ablation method and design of the active area removal pattern affect and limit the maximum light utilization efficiency ratio that can be achieved with this fabrication process. The resulting 4 cm2 translucent modules cover a range of visible light transparency from 7 to 37% with a corresponding power conversion efficiency of 5 to 13%.