“…10,11 In general, hole transport materials (HTMs) can be categorized into organic and inorganic materials. Compared with organic HTMs [such as 2,2ʹ,7,7ʹ-tetrakis[N,N-di(4methoxyphenyl)amine]-9,9ʹ-spirobifluorene (spiro-OMeTAD) 12 , (3,4ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) 13,14 , poly[bis(4-phenyl)(2,4,6trimethylphenyl)amine] (PTAA) 15 , triphenylamine (TPA), spiro-OMeTAD derivatives and others], 16,17,18,19 inorganic HTMs [like copper oxides (CuO X ), nickel oxides (NiO X ) 20 , copper iodide (CuI) 21,22 , copper thiocyanate (CuSCN) 23,24,25,26 , copper selenocyanate (CuSeCN) 27 ,…”