Two quasi-interfacial p-n junctions observed by a dual-irradiation system in perovskite solar cells oleh Mohamed I. Omer, Tao Ye, Xianqiang Li, Shaoyang Ma, Dan Wu, Lei Wei, Xiaohong Tang, Seeram Ramakrishna, Qiang Zhu, Shanxing Xiong, Jianwei Xu, Chellappan Vijila, Xizu Wang