Doping Of Organic Hole Transport Materials And Its Application In Perovskite Solar Cells

Controlling the electronic properties of organic semiconductors via doping provides the foundation for many electronic devices.The photoelectric conversion efficiency（PCE）of perovskite solar cells（PSCs）has reached 25.7%,but its stability is one of the important obstacles to its commercial development.To date,the organic semiconductors as hole transport material for most efficient PSCs use lithium bis（trifluoromethanesulfonyl）imide/oxygen as dopants to achieve high conductivity and hole mobility,which are often prone to unsatisfactory reproducibility and long-term instability.Therefore,it is urgent to explore a new idea of conductor doping of organic hole transport material and prepare large-area HTL films with ideal electrochemical performance and stable photovoltaic performance,so as to meet the commercial development of perovskite solar cells.In this paper,a novel doping method of organic hole transport material based on p-type free radical doped was developed.The specific research contents are as follows:（1）Tetrachloroethane（TeCA）-benzoyl peroxide（BPO）system was used as p-dopant for organic semiconductor.Spiro-OMe TAD,a common HTL material for perovskite solar cells,was used as the experimental subject.UV-vis absorption spectrum test show that TeCA-BPO system has successfully oxidized the hole transport material.TeCA-BPO doping system increases the conductivity of spiro-OMe TAD by four orders of magnitude.Moreover,the energy levels of spiro-OMe TAD are adjusted to better match the energy levels of perovskite layer.（2）In this paper,the TeCA-BPO system doped hole transport material was further applied to PSCs.Scanning electron microscope showed that the free radical doped hole transport layer was densely coated on the perovskite layer.Photoelectric test results show that the free radical doped hole transport layer can effectively extract and transfer charge from perovskite.The PCE of 0.16 cm² cell based on free radical doped hole transport layer is more than 18%.Since there are no by-products in the free radical doped hole transport layer,the morphology of the hole transport layer prepared with perovskite solar cells remains good after thermal aging at 80℃for 500 hours,and the thermal stability of the cells is significantly enhanced.（3）TBAPF₆ was added to the TeCA-BPO doping system,which successfully decouple the dopants from the choice of counterion by introducing larger anions.By adjusted the anions,the conductivity of the hole transport layer is significantly improved.The PCE of perovskite solar cells prepared based on anionic modified free radical doped hole transport layer is significantly improved,and the photoelectric conversion efficiency of the cells is reproducible,and the PCE of small cells with an effective area of 0.16 cm² is more than 21%.The PCE is over 16%for the modules comprising 6 series-connected sub-cells（substrate area=5 cm×5 cm,mask area=10.0 cm²）,which demonstrated a promising step forward in the development of large-scale perovskite photovoltaics.