Scalable Inverted Perovskite Solar Cells Enabled by Atomic Layer Deposition (ALD)

Abstract

Perovskite solar cells (PSCs) have managed to achieve certified power conversion efficiencies (PCEs) of 27.3%, yet losses during device upscaling remain a major roadblock in the path to commercialization. Compared with mature photovoltaic technologies such as crystalline Si and thin-film CdTe or CIGS, PSCs show a more pronounced performance loss when transitioning from small lab-scale cells to larger modules. These losses are commonly attributed to increasing series resistance (Rs) in transparent conducting oxide (TCO) substrates and challenges in maintaining film uniformity over larger areas. Here, inverted PSCs were systematically fabricated and evaluated across active areas of 0.06, 0.25, and 1 cm 2 without altering the device architecture, enabling isolation of intrinsic scaling losses. Atomic layer deposition (ALD) was employed to deposit an ultrathin nickel oxide (NiO) hole transport layer (HTL), allowing precise thickness control and highly conformal coverage compared to solution-processed nanoparticle (NP) and sol-gel NiO films. Thin film and interfacial characterization demonstrate superior coverage, electrical homogeneity, and surface wettability for ALD-NiO, resulting in an improved platform for perovskite growth. Devices incorporating ALD-NiO exhibit the smallest efficiency loss upon scaling, with PCE depreciation minimized to approximately 2% when increasing the active area from 0.06 to 1 cm 2 (19.8% to 17.6%). While the open-circuit voltage (VOC) and short-circuit current density (JSC) remained stable, the PCE loss was primarily driven by a decrease in fill factor (FF). This work identifies ALD-deposited NiO as an effective, dopant-free HTL for mitigating scalinginduced losses in inverted PSCs and provides mechanistic insight into the interplay between interfacial conformity, perovskite microstructure, and scale-related resistive limitations. Overall, this work advances understanding of scalinginduced performance losses in PSCs and underscores the potential of ALD-enabled interface control for future large-area and tandem photovoltaic applications.