The development of high efficiency solar cells relies on the management of electronic and optical properties that need to be accurately measured. As the conversion efficiencies increase, there is a concomitant electronic and photonic contribution that affects the overall performances. Here we show an optical method to quantify several transport properties of semiconducting materials and the use of multidimensional imaging techniques allows decoupling and quantifying the electronic and photonic contributions. Example of application is shown on halide perovskite thin film for which a large range of transport properties is given in the literature. We therefore optically measure pure carrier diffusion properties and evidence the contribution of optical effects such as the photon recycling as well as the photon propagation where emitted light is laterally transported without being reabsorbed. This latter effect has to be considered to avoid overestimated transport properties such as carrier mobility, diffusion length or diffusion coefficient.

In this work, the fabrication of MoOx-free semitransparent perovskite solar cells (PSC) with Power Conversion Efficiencies (PCE) up to 15.7% is reported. Firstly, opaque PSCs up to 19.7% were fabricated. Then, the rear metal contact was replaced by a highly transparent and conductive indium tin oxide (ITO) film, directly sputtered onto the hole selective layer, without any protective layer between Spiro-OMeTAD and rear ITO. To the best of our knowledge, this corresponds to the most efficient buffer layer-free semitransparent PSC ever reported. Using time-resolved photoluminescence (TRPL) technique on both sides of the semitransparent PSC, Spiro-OMeTAD/perovskite and perovskite/TiO2 interfaces were compared, confirming the great quality of Spiro-OMeTAD/perovskite interface, even after damage-less ITO sputtering, where degradation phenomena result less important than for perovskite/TiO2 one. Finally, a 4-terminal tandem was built combining semitransparent PSC with a commercially-available Aluminium Back Surface Field (Al-BSF) silicon wafer. That silicon wafer presents PCE = 19.52% (18.53% after being reduced to cell size), and 5.75% once filtered, to generate an overall 4 T tandem efficiency of 21.18% in combination with our champion large semitransparent PSC of 15.43%. It means an absolute increase of 1.66% over the original silicon wafer efficiency and a 2.65% over the cut Si cell.

Metal halide perovskites feature excellent absorption, emission and charge carrier transport properties. These materials are therefore very well suited for photovoltaics applications where there is a growing interest. Still, questions arise when looking at the unusual long carrier lifetime that, regarding the micrometric diffusion length, would imply a very low diffusion coefficient as compared to commonly used photovoltaic absorbers. In this paper, we provide an experimental insight into this long lifetime of charge carriers in slowmotion. Our approach relies on an improved model to analyze time-resolved photoluminescence decays at multiple fluence levels that includes charge carrier transport, photon recycling, and traps dynamics. The model is verified on different interface properties. Moreover, we investigate various perovskite absorbers such as mixed alloys with cesium content. For most of the perovskite based materials we analyzed, the band-to-band recombination rate remains close to the radiative limit, leading to the expected submicrosecond lifetime. The slow diffusion of charge carriers is observed with values of the diffusion coefficient D around 5x10 -3 cm 2 /s. Nonetheless, the power conversion efficiency remains high. The observations might be related to the debated coexistence of a direct and indirect bandgap slowing down the recombination process. PV characterization

Mixed halide perovskites have attracted a strong interest in the photovoltaic community as a result of their high power conversion efficiency and the solid opportunity to realize low-cost and industry-scalable technology. Light soaking represents one of the most promising approaches to reduce non-radiative recombination processes and thus to optimize device performances. Here, we investigate the effects of 1 sun illumination on state-of-the-art triple cation halide perovskite thin films Cs0.05(MA0.14, FA0.86)0.95 Pb (I0.84, Br0.16)3 by a combined optical and chemical characterization. Competitive passivation and degradation effects on perovskite transport properties have been analyzed by spectrally and time-resolved quantitative imaging luminescence analysis and by X-ray photoemission spectroscopy (XPS). We notice a clear improvement of the optoelectronic properties of the material, with a increase of the quasi fermi level splitting and a corresponding decrease of methylammonium MA+ for short (up to 1 h) light soaking time. However, after 5 h of light soaking, phase segregation and in-depth oxygen penetration lead to a decrease of the charge mobility.