Enhancing the Humidity\nStability of Perovskite Films\nthrough Interfacial Modification with Differentiated Hydrophilic Organics

Preparing high-quality perovskite films is a decisive\nstep toward\nrealizing highly efficient and stable perovskite solar cells (Pero-SCs).\nWater is a key factor affecting the stability of the Pero-SCs. Here,\nthe widely used water adsorbents chitosan, sorbitol, and sodium hyaluronate\n(NaHA) were used as hydrophilic layers on the upper interface of the\nperovskite to form a barrier against water. The water adsorbents also\npassivated defects on the surface of the perovskite active layer due\nto their −OH and −COOH functional groups. The NaHA-modified\ndevices showed the best power conversion efficiency (PCE) (PCE = 21.74%).\nAlthough the NaHA-modified Pero-SCs showed optimal photovoltaic performance,\nthe stability of the modified devices decreased due to the strong\nwater adsorption ability of NaHA, while with moderate water adsorption\nability sorbitol-modified devices exhibited good stability and PCE.\nThe devices were tested in the dark and room temperature at different\nhumidity levels for 800 h. At low humidity (25% ± 5% RH), the\nPCEs of the sorbitol- and NaHA-modified devices were maintained at\n80% and 71% of the initial values, respectively. At high humidity\n(75% ± 5% RH), the PCE was maintained at 64% and 23% of the initial\nvalues, respectively. This work provides an avenue to select adsorbents\nwith suitable water absorption ability as the interface modification\nlayer, thus reducing the water erosion of perovskite films and obtaining\nhighly stable inverted Pero-SCs.