Efficient and stable inorganic lead-free perovskite solar cell and method for preparing the same

1. An efficient and stable inorganic lead-free perovskite solar cell, comprising a conductive substrate, a poly (3,4-ethylenedioxythiophene)-poly (styrene sulfonate) layer, an inorganic lead-free CsSnI 3 perovskite layer, a fullerene layer, a bathocuproine layer, and a metal counter electrode layer arranged in order from bottom to top, wherein the inorganic lead-free CsSnI 3 perovskite layer is a CsSnI 3 perovskite layer passivated by a thioureas small-molecule organic compound.

2. The efficient and stable inorganic lead-free perovskite solar cell of claim 1 , wherein the conductive substrate is an indium tin oxide conductive glass substrate.

3. The efficient and stable inorganic lead-free perovskite solar cell of claim 1 , comprising one or more of the following features:

i. the conductive substrate has an electrical resistance of less than 6 ohm/sq, and a thickness of 140-160 nm;

ii. the poly (3,4-ethylenedioxythiophene)-poly (styrene sulfonate) layer has a thickness of 20-40 nm;

iii. the inorganic lead-free CsSnI 3 perovskite layer has a thickness of 400-500 nm;

iv. the fullerene layer has a thickness of 30-50 nm;

v. the bathocuproine layer has a thickness of 5-10 nm; and

vi. the metal counter electrode layer has a thickness of 50-70 nm.

4. The efficient and stable inorganic lead-free perovskite solar cell of claim 1 , wherein the thioureas small-molecule organic compound is selected from the group consisting of thiourea, thiosemicarbazide, and thioacetamide.

5. The efficient and stable inorganic lead-free perovskite solar cell of claim 1 , wherein the inorganic lead-free CsSnI 3 perovskite layer is prepared by a process comprising:

sequentially depositing SnI 2 , the thioureas small-molecule organic compound, and CsI on the poly (3,4-ethylenedioxythiophene)-poly (styrene sulfonate) layer, and then annealing to obtain the inorganic lead-free CsSnI 3 perovskite layer.

6. The efficient and stable inorganic lead-free perovskite solar cell of claim 1 , wherein a metal counter electrode in the metal counter electrode layer is copper counter electrode or gold counter electrode.

7. A method for preparing the efficient and stable inorganic lead-free perovskite solar cell of claim 1 , comprising the following steps:

(1) pretreating the conductive substrate;

(2) spin-coating a poly (3,4-ethylenedioxythiophene)-poly (styrene sulfonate) aqueous solution on the conductive substrate, and annealing to obtain the poly (3,4-ethylenedioxythiophene)-poly (styrene sulfonate) layer;

(3) using SnI 2 , the thioureas small-molecule organic compound and CsI as raw materials, depositing SnI 2 , the thioureas small-molecule organic compound, and CsI on the poly (3,4-ethylenedioxythiophene)-poly (styrene sulfonate) layer in sequence by a vacuum thermal evaporation, and then annealing to obtain an inorganic lead-free CsSnI 3 perovskite layer; and

(4) sequentially depositing a fullerene layer, a bathocuproine layer and a metal counter electrode layer on the inorganic lead-free CsSnI 3 perovskite layer by a vacuum thermal evaporation to obtain an inorganic lead-free perovskite solar cell.

8. The method of claim 7 , wherein the method is conducted under conditions comprising one or more of the following items:

i. in step (1), the conductive substrate is pretreated as follows: etching, washing, and drying the conductive substrate, and finally subjecting the conductive substrate to an ultraviolet ozone treatment;

ii. in step (2), the poly (3,4-ethylenedioxythiophene)-poly (styrene sulfonate) aqueous solution is spin coated on the conductive substrate using a spin coater at a spin-coating speed of 2000-3000 rpm for 30-40 s; and

iii. in step (2), the annealing is conducted at a temperature of 80-120° C. for 5-15 min.

9. The method of claim 7 , wherein step (3) is conducted under conditions comprising one or more of the following items:

i. the thermal vacuum evaporation is conducted at a vacuum degree of less than 1×10 −5 Pa, during which SnI 2 is evaporated at a heating temperature of 300-350° C. and an evaporation rate of 0.1-0.2 nm/s, the thioureas small-molecule organic compound is evaporated at a heating temperature of 70-100° C. and an evaporation rate of 0.1-0.2 nm/s, and CsI is evaporated at a heating temperature of 550-600° C. and an evaporation rate of 0.2-0.5 nm/s;

ii. a molar ratio of CsI to SnI 2 is in a range of 1: (1-1.3), a molar ratio of the thioureas small-molecule organic compound to CsI is in a range of 1: (45-55), a molar ratio of CsI to SnI 2 is 1:1.2, and a molar ratio of the thioureas small-molecule organic compound to CsI is 1:50;

iii. CsI has a purity of 99.9%, and SnI 2 has a purity of 99.99%; and

iv. the annealing is conducted at a temperature of 120-140° C. for 10-20 min.

10. The method of claim 7 , wherein step (4) is conducted as follows:

under a vacuum degree of less than 1×10 −5 Pa, evaporating fullerene at an evaporation rate of 0.1-0.3 nm/s, and depositing on the inorganic lead-free CsSnI 3 perovskite layer to obtain a fullerene layer; then evaporating bathocuproine at an evaporation rate of 0.05-0.3 nm/s, and depositing on the fullerene layer to obtain a bathocuproine layer; finally evaporating a metal at an evaporation rate of 0.2-0.7 nm/s, and depositing on the bathocuproine layer to obtain an inorganic lead-free perovskite solar cell.