Improving the stability of perovskite solar cells and modules by interface and grain boundary passivation

Promovendus/a: Xin Zhang

Promotor(en): Prof. dr. ir. Jozef Poortmans, Prof. Yiqiang Zhan

Thanks to the excellent optoelectronic properties of perovskite, including direct band gap, high absorption coefficient, long carrier lifetime, tunable band gaps, etc., we have witnessed a rapid development of perovskite solar cells (PSCs) over the last decade. Highly efficient PSCs are often obtained based on the n-i-p device configuration and the perovskite layers prepared by the anti-solvent method. However, the anti-solvent is often toxic and this method is not compatible with device upscaling. Gas-quenching, as an alternative to anti-solvent, uses a non-toxic and inexpensive gas instead of a toxic antisolvent and has the merits of easy control, highly reproducible, upscaling compatible, etc. Nevertheless, the performance of gas-quenched inverted p-i-n PSCs is still lagging behind that of state-of-the-art n-i-p PSCs. This dissertation therefore concentrates on understanding and improving the performance of gas-quenched p-i-n PSCs and perovskite modules.

Optimizing the bulk quality and the interfacial properties of perovskite films is crucial for achieving high-efficiency PSCs. We stablish a baseline platform based on the optimization of perovskite composition and the selection of hole transport layers, with a PCE of about 19% achieved based on the Cs0.1FA0.9PbI2.7Br0.3 perovskite. An integrated strategy is further proposed to upgrade both the surface and bulk properties of the gas-quenched perovskite films. As a result, a significant PCE boost is obtained with an excellent PCE of 22.3%. Meanwhile, unstable operational behavior of sputtered NiOx-based Cs0.1FA0.9PbI2.855Br0.145 PSCs is improved by the top surface modification. Following that, we simultaneously optimize the two interfaces adjacent to the Cs0.1FA0.9PbI2.855Br0.145 perovskite. An in-depth understanding is obtained that the upper interface modification can effectively reduce the non-radiative recombination centers and facilitate the extraction of photogenerated electrons. While the buried interface modification is beneficial to the transport of photogenerated holes via a more matched energy level alignment. Consequently, small-area (0.13 cm2) highly efficient gas-quenched PSCs with a PCE of 24.3% and larger area (> 3.6 cm2) perovskite modules with a PCE of 22.6% are demonstrated.