I have an 8 week old puppy that refuses to go potty outside. any housebreaking tips that really work?

she's an 8 week old border collie mix. anytime i take her outside, she refuses to go to the bathroom. after spending 15-20 minutes outside, we go back inside and she goes on the floor. i've tried crate training her and also using a puppy pad. nothing is working. it's cold outside, and my boyfriend thinks she might not like going in the cold. i need help training her. any useful tips would help.