Clarifying the structural basis and microscopic mechanism lying behind electronic properties of molecular semiconductors is of paramount importance in further material design to enhance the performance of perovskite solar cells. In this paper, three conjugated quasilinear segments of 9,9-dimethyl-9H-fluorene, 9,9-dimethyl-2,7-diphenyl-9H-fluorene, and 2,6-diphenyldithieno­[3,2-b:2′,3′-d]­thiophene are end-capped with two bis­(4-methoxyphenyl)­amino groups for structurally simple molecular semiconductors Z1, Z2, and Z3, which crystallize in the monoclinic P 21/n, triclinic P1̅, and monoclinic C 2/ c space groups, respectively. The modes and energies of intermolecular noncovalent interactions in various closely packed dimers extracted from single crystals are computed based on the quantum theory of atoms in molecules and energy decomposition analysis. Transfer integrals, reorganization energies, and center-of-mass distances in these dimers as well as band structures of single crystals are also calculated to define the theoretical limit of hole transport and microscopic transport pictures. Joint X-ray diffraction and space-charge-limiting current measurements on solution-deposited films suggest the dominant role of crystallinity in thin-film hole mobility. Photoelectron spectroscopy and photoluminescence measurements show that an enhanced interfacial interaction between the perovskite and Z3 could attenuate the adverse impact of reducing the energetic driving force of hole extraction. Our comparative studies show that the molecular semiconductor Z3 with a properly aligned highest occupied molecular orbital energy level and a high thin-film mobility can be employed for efficient perovskite solar cells, achieving a good power conversion efficiency of 20.84%, which is even higher than that of 20.42% for the spiro-OMeTAD control.

Ionic organic-inorganic hybrid lead halide perovskites are prone to degrade at elevated temperatures, especially in the presence of water moisture. This grand challenge heavily impedes the outdoor application of high-efficiency...

Despite the efficiency comparable to crystalline silicon photovoltaics, it is still a severe concern on the long-term stability under the stress of heat, light, and bias potential for perovskite solar cell (PSC).Here, we report a triple aza[6]helicene-based molecular semiconductor (TBTA[6]H) characteristic of a fully fused conjugated backbone. TBTA[6]H presents superior solubility and glass-transition temperature (T g ). An airdoped composite of TBTA[6]H with a high electrical conductivity of 353 μS cm −1 is still featured by a T g of 112 °C, enabling the fabrication of 22% efficiency, 85 °C durable PSCs. The TBTA[6]H composite not only exhibits an excellent morphology stability at 85 °C in PSCs, but also remarkably attenuates the thermal degradation of photoactive perovskite layer. The cell with TBTA[6]H also displays an excellent operation stability under the continuous full sunlight soaking at 55 °C.

Organic-inorganic hybrid perovskites in high-efficiency solar cells are prone to degradation at elevated temperatures, especially in the presence of water moisture. A hole-transporting conjugated copolymer (abbreviated as p-NP-E) characteristic of alternating N-annulated perylene and 3,4-ethylenedioxythiophene backbones, to achieve thermostable perovskite solar cells (PSCs) via controlling gas permeation and thus perovskite decomposition is reported. p-NP-E can be conveniently prepared via Pd-catalyzed direct arylation polycondensation. The air-doped p-NP-E composite film containing nonvolatile 4-tert-butylpyridinium bis(trifluoromethanesulfonyl)imide presents a higher hole mobility and an improved conductivity in comparison with the control based on the state-of-the-art polymer, p-TAA, leading to more efficient PSCs. More critically, the p-NP-E based hole transport layer is not only morphologically more heat-resistant, but also features a lower solubility coefficient and diffusion coefficient of both environmental water molecules and gaseous products such as CH 3 I and CH 3 NH 2 from the thermal decomposition of perovskite, enabling the fabrication of 21.7%-efficiency, 85 °C durable solar cells.

Judicious tailoring of a robust interlayer is central to maintain the durable operation of optoelectronic devices. In this paper, an ultrathin, compact, and uniform PbI2 shell on the surface of perovskite via the method of ZnI2 aided in situ transformation is produced. The resultant PbI2 interlayer can prolong the excited‐state lifetime of perovskite and attenuate the recombination kinetics of separated charges, leading to an improvement of power conversion efficiency up to 22.5% for perovskite solar cells (PSCs) at the AM 1.5G conditions. Moreover, the PSC with PbI2 interlayer exhibits an enhanced thermostability, retaining 87% of initial efficiency after aging at 60 °C for 1000 h.