Recent Advances in Nanostructured Inorganic Hole-Transporting Materials for Perovskite Solar Cells

Abstract

Organic−inorganic halide perovskite solar cells (PSCs) have received particular attention in the last decade because of the high−power conversion efficiencies (PCEs), facile fabrication route and low cost. However, one of the most crucial obstacles to hindering the commercialization of PSCs is the instability issue, which is mainly caused by the inferior quality of the perovskite films and the poor tolerance of organic hole−transporting layer (HTL) against heat and moisture. Inorganic HTL materials are regarded as promising alternatives to replace organic counterparts for stable PSCs due to the high chemical stability, wide band gap, high light transmittance and low cost. In particular, nanostructure construction is reported to be an effective strategy to boost the hole transfer capability of inorganic HTLs and then enhance the PCEs of PSCs. Herein, the recent advances in the design and fabrication of nanostructured inorganic materials as HTLs for PSCs are reviewed by highlighting the superiority of nanostructured inorganic HTLs over organic counterparts in terms of moisture and heat tolerance, hole transfer capability and light transmittance. Furthermore, several strategies to boost the performance of inorganic HTLs are proposed, including fabrication route design, functional/selectively doping, morphology control, nanocomposite construction, etc. Finally, the challenges and future research directions about nanostructured inorganic HTL−based PSCs are provided and discussed. This review presents helpful guidelines for the design and fabrication of high−efficiency and durable inorganic HTL−based PSCs.

Additive Engineering for Mixed Lead–Tin Narrow-Band-Gap Perovskite Solar Cells: Recent Advances and Perspectives

“…Nevertheless, silicon solar cells suffered from high-cost fabrication procedures and raw materials as well as environmentally harmful byproducts during the Si fabrication process . The second-generation solar cells are gallium arsenide (GaAs), cadmium telluride (CdTe), and copper indium gallium selenide (CIGS) thin-film solar cells, which exhibit high PCEs and stable device performance. − Nevertheless, the elements in the key materials used in thin-film solar cells are toxic and/or rare, strongly limiting the practical applications. , …”

High Fill Factor and Reduced Hysteresis Perovskite Solar Cells Using Small-Molecule-Engineered Nickel Oxide as the Hole Transport Layer

“…24 Further examples of NiO x functionalization have been summarized in recent reviews. 25,26 In this work, we explore 4-dimethylaminopyridine (DMAP), a bifunctional molecule assuring strong interaction with both the HTL and the perovskite layer, as the passivation agent for sol−gel-processed NiO x HTLs. To enhance the conductivity of NiO x , 5 mol % of Cu dopant is used 27 and the resulting HTL is therefore referred to as Cu:NiO x .…”

“…As typical examples, diethanolamine and ferrocenedicarboxylic acid have been proposed, interacting via the amine or carboxylic acid function with the NiO x surface, respectively. , In another example, by bridging the NiO x nanocrystalline film with the perovskite layer via a self-assembled monolayer consisting of two types of molecules comprising carbazole and phosphonic acid groups, interfacial recombination was mitigated and hole extraction improved, resulting in an efficiency of 24.7% for flexible all-perovskite tandem solar cells . Further examples of NiO x functionalization have been summarized in recent reviews. , …”

Iodide/triiodide redox shuttle-based additives for high-performance perovskite solar cells by simultaneously passivating the cation and anion defects

“…26,27 To tackle the crucial issues of point defects in organic-inorganic Pb/I-based PSCs, tremendous attempts have been made recently such as additive engineering and surface passivation. [28][29][30][31][32][33][34][35][36][37][38][39][40] Additives with functional groups such as O-, N-, or S-donors introduced into the perovskite precursor solution can coordinate with unpaired Pb 2+ and stabilize Pb atoms in the perovskite lattice. 41 In particular, metal/organic halide salt additives such as NaX, CsX, KX, RbX, MAX, and FAX (where X = F, Cl, Br) have been added in to the precursor solution and/or the lattice of halide perovskites, showing two main functions: (1) cations with a suitable radius can occupy the A-site to stabilize the perovskite structure and adjust its band gaps and photoelectric properties and (2) anions anchor Pb 2+ through hydrogen bonds to inhibit the movement and immigration of Pb 2+ cations.…”