Polymer, organic solar cell comprising polymer, perovskite solar cell comprising polymer

A perovskite solar cell comprising:

• a first electrode and a second electrode disposed facing each other;
• and
• an electron transport layer, a perovskite layer, and a hole transport layer which are stacked between the first electrode and the second electrode,
• wherein the hole transport layer comprises a polymer for a hole transport layer of a perovskite solar cell which is represented by the following Structural Formula 1:
• wherein in Structural Formula 1,
• X1, X2, X3 and X4 are each independently O, S, Se, NH, or NR′,
• R1, R2, R3 and R4 are each independently an alkyl group having 1 to 50 carbon atoms, an aryl group having 6 to 50 carbon atoms, or —COOR′,
• A1, A2, A3, and A4 are each independently H, F, CN, or —COOR′,
• R′ is an alkyl group having 1 to 50 carbon atoms or an aryl group having 6 to 50 carbon atoms, and
• n is an integer ranging from 1 to 1000,
• wherein the polymer for a hole transport layer has a crystalline coherence length (CCL) in the range of 25 Å to 30 Å.