Improved Efficiency of Perovskite Solar Cells with Low-Temperature-Processed Carbon by Introduction of a Doping-Free Polymeric Hole Conductor

Low-temperature-processed carbon-based perovskite solar cells (C-PSCs) are promising photovoltaic devices, because of their good stability, low cost, and simple preparation methods, which allow for scalable processing. Herein, C-PSCs with the n-i-p structure are prepared, using a SnO2 nanoparticles film as the electron-selective contact, MAPbI(3) perovskite as the intrinsic absorber layer (MA = methylammonium), and a carbon layer as the hole-selective layer and conductor. Carbon is, however, not an ideal hole-selective layer and it is found that improved solar cell performance can be obtained by introducing a polymeric hole conductor between the perovskite and the carbon layer. Specifically, undoped poly(3-hexylthiophene) (P3HT) is used for this purpose, as it is stable and highly hydrophobic. For ITO/SnO2/MAPbI(3)/carbon devices, a solar cell efficiency of up to 12.8% is obtained, increasing up to 15.7% with the inclusion of a P3HT layer, which increases open-circuit potential, photocurrent, and fill factor (FF). In comparison, ITO/SnO2/MAPbI(3)/P3HT/Au devices performed rather poorly (up to 11.7%). Encouraging stability is obtained for unencapsulated C-PSC devices: P3HT/carbon devices do not show any degradation in solar cell performance upon storage for 1 month in low humidity, while they maintain 70% of their initial efficiency after 900 h at 82 degrees C in air

Enhanced Thermal Stability of Low-Temperature Processed Carbon-Based Perovskite Solar Cells by a Combined Antisolvent/Polymer Deposition Method

Low-temperature processed carbon-based perovskite solar cells have received great attention due to low-cost, high stability, and simple preparation processes that can be employed in large-scale manufacturing. Carbon paste is deposited by techniques such as doctor blading or screen printing. However, solvents from this paste can damage the perovskite or underlying layers resulting in poor performance of solar cells. Furthermore, carbon is not an ideal hole-selective contact. To overcome these issues, the antisolvent treatment is combined with the deposition of a polymeric hole conductor. Specifically, poly(3-hexylthiophene) (P3HT), added into the chlorobenzene antisolvent, improves perovskite morphology and reduces interfacial carrier recombination. As a result, the power conversion efficiency (PCE) of solar cells with the device structure SnO2/MAPbI3/P3HT/carbon increases to 12.16% from 10.6% of pristine devices without P3HT, using pure antisolvent. For poly(triarylamine) hole conductor in the same method, PCE improves only slightly to 11.1%. After 260 h of thermal stress at 82 °C, the P3HT-additive devices improve PCE up to 13.2% in air and maintain 91% of their initial efficiency over 800 h.De två första författarna delar förstaförfattarskapet</p

Reduced hysteresis and enhanced air stability of low-temperature processed carbon-based perovskite solar cells by surface modification

Low temperature processed carbon-based perovskite solar cells (C-PSCs) have gained great interest because of low cost and ease of fabrication. By replacing the Au electrode with carbon, stable solar cells suited for mass-production process can be made. However, power conversion efficiencies (PCEs) of C-PSCs still lag behind that of PSCs with Au contact.Here we explore low temperature (&lt;= 150 degrees C) processed C-PSCs with, where a two-step method is used to prepare mixed-ion lead perovskite films, with tin oxide (SnO2) electron transport layer, poly(3-hexylthiophene-2,5-diyl) (P3HT) hole transport layer and carbon electrode, resulting in devices with a PCE of 14.0%. Moreover, hexyl trimethylammonium bromide (HTAB) was introduced to improve the interface between perovskite and P3HT. Perovskite grains were remarkably enlarged into micrometer-size and defects were reduced. As a result, a champion PCE of 16.1% was obtained, mainly due to enhanced fill factor from 0.67 to 0.73. The interface modification by HTAB molecule is an effective way to passivate the perovskite defects and facilitate the carrier transport at the perovskite/HTL interface. Unencapsulated devices showed excellent stability over 1500 h stored under ambient air (relative humidity -50 +/- 10%)

Simple Method for Efficient Slot-Die Coating of MAPbI(3) Perovskite Thin Films in Ambient Air Conditions

Scalable methods for deposition of lead halide perovskite thin films are required to enable commercialization of the highly promising perovskite photovoltaics. Here, we have developed a slot-die coating process under ambient conditions for methylammonium lead iodide (MAPbI(3)) perovskite on heated substrates (about 90 degrees C on the substrate surface). Dense, highly crystalline perovskite films with large grains (100-200 mu m) were obtained by careful adjustment of the deposition parameters, using solutions that are similar but more dilute than those used in typical spin-coating procedures. Without any further after treatments, such as antisolvent treatment or vapor annealing, we achieved power conversion efficiencies up of 14.5% for devices with the following structure: conducting tin oxide glass (FTO)/TiO2/MAPbI(3)/spiro-MeOTAD/Au. The performance was limited by the significant roughness of the deposited films, resulting from the hot-casting method, and the relatively high deposition temperature, which led to a defect-rich surface due to loss of MAI