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Chemical doping is adopted to tune the work function and electrical conductivity of carbon counter electrode (CE) in HTM-free organometallic halide perovskite solar cells (PSCs). In this work, the boron and phosphorus co-doped carbon (BPC) CE is constructed by coating a B doped carbon layer onto the P-doped carbon (PC). The work function of BPC CE with B/P co-doping (B: 2.68 at.%, P: 2.23 at.%) is thus regulated to 5.12 eV from the 5.01 eV of pure carbon and 4.81 eV of PC, and the sheet resistance is modulated to 8.41 Ω sq −1 from 14.75 Ω sq −1 of pure carbon and 7.89 Ω sq −1 of PC. As a consequence, the BPC-based PSCs deliver a power conversion efficiency of 6.78%, higher than those of pristine carbon (3.72%), PC (5.39%) and BC (5.20%) based PSCs, and even comparable to that of conventional Au-based device (7.22%), due to the enhanced hole extraction ability and the maintained high electronic conductivity. Moreover, the good stability in ambient condition over a period of 720 h is also demonstrated in the BPC-based PSCs. The successful application of BPC CE in PSCs shows a promising way for fabricating low-cost, large-scale and highly efficient PSCs in future.

Photoelectrochemical electrodes have been prepared by chemical deposit of quantum sized PbS particles (Q-PbS) on TiO 2 nanocrystalline films and followed by the modification of such electrodes with thiols. The photoelectrochemical properties have been studied. The results show that Q-PbS modified TiO 2 electrodes generate photocurrent as high as 542.5 μA/cm 2 under irradiation of a 400 nm light, but it undergoes photodegradation. The modification with thiols leads to an improvement in terms of increased photostability, although the photocurrent decreases due to the resistance brought about by the carbon chains of thiols.

Self-assembled films (SA films) of 3,4,9,10-perylenetetracarboxylic acid (PTA) (Film P) and II B group metal-ion-bridged PTA (Film PMP, M=Zn 2+ , Cd 2+ , or Hg 2+ ) were fabricated on nanocrystalline TiO 2 electrodes and characterized with UV–VIS and IR spectra and XPS. Compared with Film P sensitized solar cell, Gratzel cells based on individual PMP electrodes are more efficient regarding photocurrent generation. Synchrotron radiation photoelectron spectroscopy (SRPES) study reveals that those HOMO energy levels of PMP films are greater than that of Film P. The higher HOMO energy levels will lead to higher excited state energy levels that benefit electron injection, and hence, increase efficiencies for photocurrent generation. In view of the invariable valence of Zn 2+ , Cd 2+ , and Hg 2+ ions, electron injection should be attributed to ligand, but not to the central metal ions, like the case of Ru(II)–bipyridyl complex.