ALD NiOX hole transport layers for semi-transparent perovskite solar cells with average visible transmittance exceeding 50%

Abstract All-inorganic CsPbBr3 semi-transparent perovskite solar cells (PSCs) hold significant promise for optoelectronic applications. However, the performance improvement is hindered by challenges such as poor interfacial compatibility between the hole transport layer (HTL) and perovskite, limitations of conventional fabrication methods, and intrinsic defects in CsPbBr3. To address these issues, we propose a mild and efficient device fabrication strategy. Ultrapure water is introduced as a co-reactant in an atomic layer deposition (ALD) process to grow a nickel oxide (NiOX) HTL compatible for n-i-p structured devices. The hydroxyl groups derived from water molecules provide abundant adsorption sites, ensuring uniform and conformal film growth. By precisely controlling the water pulse duration, the Ni3+ content and work function of the NiOX layer can be finely tuned. Concurrently, a 2-phenylethylammonium bromide (PEABr) surface passivation layer deposited via ultrasonic spray coating effectively protects the CsPbBr3 from exposure to high-temperature water vapor during ALD process. This passivation layer simultaneously replenishes Br- vacancies and passivates undercoordinated Pb2+ species at perovskite surface. As a result, small-area CsPbBr3 PSCs fabricated using this strategy achieve a power conversion efficiency (PCE) of 7.00% and large-area devices demonstrate an efficiency of 3.47%, highlighting the excellent scalability and application potential of this approach.