Managing transparency through polymer/perovskite blending: A route toward thermostable and highly efficient, semi-transparent solar cells

Semi-transparent perovskite-based solar cells feature competitive levels of transparency and efficiency, envisioning their future application in building integrated photovoltaics. However, complex processing conditions and thermal stability, inherent of hybrid halide perovskite materials, remain urgent issues to be solved. Herein, the interaction with perovskite precursors and transparency in the visible range of cellulose polymer are explored for the realization of semi-transparent perovskite-polymer composite. Hydroxyethyl cellulose inclusion in CH3NH3PbI3 was found to have several beneficial effects, namely, to simplify processing conditions, to improve the average visible transmittance of ~44% and, foremost, to enhance the thermal stability without compromising photovoltaic performances of semi-transparent perovskite solar cells. A maximum light utilization efficiency (LUE) of 2.4% corresponding to a power conversion efficiency of 11.6% was demonstrated, which is in the range usually required for window applications, positioning these semi-transparent solar cells among the most efficient ones reported to date.